1. Field of the Invention
This invention relates to a process for rapidly forming a water-proof, moisture-proof or gas-proof rubber asphalt solid layer on a substrate surface by separately spraying a highly concentrated rubber-asphalt emulsion and a coagulant in the state of mist by means of a spraying machine to continuously contact and mix them together in the space between the spraying machine and the substrate surface and on the substrate surface.
2. Description of the Prior Art
A rubber-asphalt emulsion is mainly used as a water-proof material, and its application is usually practised by coating it on the substrate surface by means of a brush, trowel or the like. Since this process is limited in one-coat amount, the number of applications must be increased in this type of coating which requires a considerable coating thickness, and this is troublesome. If a large quantity of coating material is applied at once, a long period of time is necessary for drying it, the coating formed is apt to lack uniformity, and there can appear cracks, unevenness and the like sometimes. If a vertical wall or a ceiling is coated with a high flow type rubber-asphalt emulsion in consideration of workability, the emulsion drips down in the course of coating and just after coating to make various troubles. Accordingly, coating by means of a trowel or brush is poor in workability, complicated and unsuitable for the coating of broad area. Even in the case of such a coating process the one-coat amount can be increased by adding a mild coagulant such as sodium silicofluoride to a rubber-asphalt emulsion, but this method is limited in working time before coagulation, and it is necessary to blend a coagulant with the emulsion just before use, so that this method is troublesome and cannot be said to be effective.
A process which was developed with the aim of overcoming these difficulties is disclosed in, for example, Japanese Patent Application Kokai (Laid-Open) No. 31606/75. This process comprises spraying a stream of (A) highly concentrated bituminous substance-latex mixture and a stream of (B) an emulsion mixture comprising a coagulant and an aqueous emulsion containing at least one member selected from the group consisting of bituminous substances, oils and latexes while continuously mixing the two streams. In this process, the emulsion mixture (B) is quite instable because it has a high concentration and contains a coagulant, so that the nozzle of a spraying machine is apt to clog. Furthermore, the kind of coagulant usable in this process is limited in order to prevent the coagulation of the emulsion mixture (B) itself, due to which it takes a longer period of time until the formation of solid layer.
The present inventors conducted repeated studies about these points to find that a rubber-asphalt solid layer can be formed on the substrate surface without any of the above-mentioned troubles by a combined technique comprising using a rubber-asphalt emulsion having a total solid content of 70% or more, spraying a coagulant in the form of an aqueous solution not mixed with an emulsion, spraying them separately by means of airless type spraying machines, and contacting and mixing them together in the space between the spraying machine and the surface of a substrate to be coated and on the substrate surface.